The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Process control systems, like those used in chemical, petroleum, industrial or other process plants to manufacture, refine, transform, generate, or produce physical materials or products, typically include one or more process controllers communicatively coupled to one or more field devices via analog, digital or combined analog/digital buses, or via a wireless communication link or network. The field devices, which may be, for example, valves, valve positioners, actuators, switches and transmitters (e.g., temperature, pressure, level and flow rate sensors), are located within the process environment and generally perform physical or process control functions such as opening or closing valves, measuring process parameters such as pressure, temperature, etc., and the like to control one or more process executing within the process plant or system.
Smart field devices, such as the field devices conforming to the well-known Fieldbus protocol, may also perform control calculations, alarming functions, and other control functions commonly implemented within the controller. The process controllers, which are also typically located within the plant environment, receive signals indicative of process measurements made by the field devices and/or other information pertaining to the field devices and execute a controller application that runs, for example, different control modules which make process control decisions, generate control signals based on the received information and coordinate with the control modules or blocks being performed in the field devices, such as HART®, WirelessHART®, and FOUNDATION® Fieldbus field devices. The control modules in the controller send the control signals over the communication lines or links to the field devices to thereby control the operation of at least a portion of the process plant or system, e.g., to control at least a portion of one or more industrial processes running or executing within the plant or system. I/O devices, which are also typically located within the plant environment, typically are disposed between a controller and one or more field devices, and enable communications there between, e.g. by converting electrical signals into digital values and vice versa. Field devices, controllers, and I/O devices are generally located, disposed, or installed in a field environment of a process control system or plant.
Supercapacitors may be utilized in process control systems for a variety of purposes such as to provide backup power for field devices during a power outage or power shortage. That is, the input power supply used to power the field devices may be a variable power supply, such as a solar panel, and may sometimes fail to provide power. When the input power supply is functioning properly, the input power supply will supply power to field devices and will also supply power to the supercapacitor. Accordingly, the supercapacitor may be charged, e.g., to a particular voltage required to power the corresponding field device, while the input power supply is available. Then, when the input power supply no longer provides sufficient power, the supercapacitor may be discharged in order to power the field device. For example, upon loss of power, the supercapacitor may supply power to an actuator to drive a valve into a preconfigured “safe” position during a power outage and/or power shortage. In this way, the safety of the process control system may be maintained even during power outages and/or power shortages. More generally, supercapacitors may be used in process control systems as back-up storage devices or primary power storage devices, in a variety of applications.
Upon aging, which involves chemical degradation, a supercapacitor can no longer provide backup power to a field device in a process control system. Generally speaking, supercapacitors age more quickly when operating at high temperatures. However, in many instances, devices in process control systems must operate at relatively high ambient temperatures.